The ordinary telephone in general use, commonly termed a POT (plain old telephone) comprises a hand set and a keypad and may contain a display for visually displaying phone numbers, date and time, caller ID, etc. Such telephones are connected to other telephones through a network including hard wires and wireless links whereby users talk to other users directly or leave messages.
Computers that can be connected to the telephone system are also in widespread use, the communications link often being a modem and associated programming that connect the computer to other computers via the Internet through the services of an Internet Service Provider (ISP).
Both of these systems require connections to be made by an interfacing unit in the local telephone exchange. Thus, all present telephone calls and computer connections to the Internet pass through a local telephone exchange, which means that each connection must at some point include a telephone number and be individually dialed before the connection can be made. This requirement places a severe restriction on the ability to communicate with a large number of telephones and easy access to the Internet.